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The Case

A male presents to the emergency department with increasing pain to the left groin region for 3 days. He notes that he injects heroin daily and has been injecting into his femoral vein region for the past few weeks. He also notes fever and chills since last night.

Vitals: T 101.5 HR 120 BP 101/53 RR 14 O2 100% on room air

The patient's exam is notable for a 3 cm indurated, erythematous, and exquisitely tender mass directly over the femoral vessel complex at the level of the inguinal ligament. Trace edema is also noted in the left foot and ankle. A bedside ultrasound was performed:

Short axis view along femoral vessel complex over mass. Structures seen here were non compressible

Short axis view along femoral vessel complex over mass, with color doppler.

Structure identification from previous ultrasound views.

As seen above, no abscess was identified and the two hypoechoic structures of interest were determined to be a reactive lymph node (superficial) and the femoral vein with clot (deep). Given fever and signs to suggest developing sepsis, the presumptive diagnosis of septic thrombophlebitis was made at this time and the patient was initiated on parenteral antibiotic therapy with vancomycin and zosyn. She was also resuscitated aggressively with fluids with excellent response.

A formal lower extremity venous ultrasound study was obtained which then revealed significant femoral venous thrombosis with distal extension. Anticoagulation with Lovenox was initiated and the patient was admitted to the hospital for further management. The patient later grew out MSSA in his blood cultures which confirmed the diagnosis.

Septic Thrombophlebitis

Septic thrombophlebitis is a condition that is characterized by venous thrombosis, inflammation and bacteremia. It has a wide range of presentation from local benign infection to septic shock. There are a multitude of distinct clinical conditions that have been described previously, depending on which venous structure is involved, however the basic pathophysiology remains the same. The most common locations this entity is seen includes:

Since IV drug users frequently inject smaller veins in their arms and legs, these vessels eventually become sclerosed and they turn to larger vessels such as the femoral, axillary and neck increasingly for injection preference. With repeated use, these vessels become injured, leading to hematoma formation, thrombosis and potentially superinfection. At this point septic thrombophlebitis can develop, however other complications can be seen such as mycotic aneurysm or traumatic arteriovenous fistula.

Clinical findings: Local pain, swelling and redness over injection site is predominately seen which can often appear as a simple abscess or cellulitis. Occasionally, these infections can be limited to deeper venous structures without considerable superficial skin changes. Fever is usually present in about 50% of these patients.

Work up:

Labs: CBC, basic chemistry, lactic acid, coags

Blood cultures

Imaging: Ultrasound or CT with IV contrast

Treatment: The treatment of peripheral septic thrombophlebitis remains controversial. While parenteral antibiotic therapy is standard of care, the value of anticoagulation use has not been established. It may be reasonable to consider anticoagulation if there is significant clot burden or extension in a deep vessel.

The theoretical concern with anticoagulation is that if there has been septic embolic events to the lungs or brain, with subsequent mycotic aneurysm formation, then there is a potential risk for bleeding from these sites. The entire clinical picture must be taken into account, including complete physical exam, symptoms and comorbidities before considering anticoagulation.

Conclusion

You always need to maintain a high suspicion for serious infection in the IV drug user, even when the infection may seem superficial and benign at first. Don't be afraid to slap on your ultrasound probe to get more information to assist with your clinical decision making and help guide you to the proper diagnosis.

I recommend listening to a great lecture by Andy Neill on Approach to the IV Drug User at Emergency Medicine Ireland for further learning on this topic.